Discontinuing Ventilatory Support



Discontinuing Ventilatory Support



Objectives


Upon the completion of the chapter activities and content review topics, the student should be able to:


1. Evaluate a patient for readiness for a spontaneous breathing trial.


2. Perform a spontaneous breathing trial procedure.


3. Describe the guidelines for extubation.


4. List the acceptable weaning indices used to predict a patient’s readiness for discontinuation of ventilatory support.


5. Determine an appropriate weaning mode for a patient.


6. Perform the weaning procedure.


7. Describe factors that may lead to ventilator dependence.


8. Perform a terminal weaning procedure.



Key Terms










Removing a patient from ventilatory support may range from a routine procedure that takes minutes to the need for a systematic approach that takes days to weeks. However rapid or time consuming the undertaking, discontinuation of ventilatory support requires the evaluation of a patient’s physiologic and psychological status and, at times, even requires ethical considerations. Physiologic parameters for weaning and extubation are provided in Table 25-1.



TABLE 25-1


Physiologic Parameters for Weaning and Extubation of Adults









































































Parameter Acceptable Value
VENTILATORY PERFORMANCE AND MUSCLE STRENGTH
VC >15 mL/kg (IBW)
VE <10–15 L/min
Vt >4–6 mL/kg (IBW)
f <35 breaths/min
f/Vt <60–105 breaths/min/L (spontaneously breathing patient)
Ventilatory pattern Synchronous and stable
Plmax (up to 20-s measurement from RV) <–20 to –30 cm H2O
MEASUREMENT OF DRIVE TO BREATHE
P0.1 >–6 cm H2O
Measurement and estimation of WOB
WOB* <0.8 J/L
Oxygen cost of breathing* <15% of total image
Dynamic compliance (Cd) >25 mL/cm H2O
VD/Vt <0.6
CROP index >13 mL/breaths/min
MEASUREMENT OF ADEQUACY OF OXYGENATION
PaO2 ≥60 mm Hg (FiO2 <0.4)
PEEP ≤5–8 cm H2O
PaO2/FiO2 >250 mm Hg (consider at 150–200 mm Hg)
PaO2/PAO2 >0.47
P(A-a)O2 <350 mm Hg (FiO2 =1)
% image <20% to 30%


image


%QS/QT, Percent shunt; CROP, compliance, respiratory rate, oxygenation, and inspiratory pressure; f, respiratory rate; f/Vt, rapid shallow breathing index; FiO2, fractional inspired O2; IBW, ideal body weight; P(A-a)O2, alveolar-to-arterial partial pressure of O2; P0.1, pressure on inspiration measured at 100 milliseconds (ms); PaO2, partial pressure of O2 in the arteries; PaO2/FiO2 (P/F), ratio of partial pressure of O2 (PO2) in the arteries to FiO2; PaO2/PAO2, ratio of arterial PO2 to alveolar PO2; PEEP, positive end-expiratory pressure; Plmax, maximum inspiratory pressure; RV, residual volume; VC, vital capacity; VD/VT, ratio of dead space to tidal volume; image, minute ventilation; image, oxygen (O2) consumption per minute; Vt, tidal volume.


*Actual measure of work of breathing (WOB).


(From Cairo JM: Pilbeam’s mechanical ventilation, ed 5, St. Louis, 2011, MO, Mosby.)



image Tip Be familiar with ventilator “lingo” at your facility. A spontaneous breathing trial (SBT) and weaning are not the same thing. Be succinct with your wording, and keep with department terminology.


Many terms such as gradual withdrawal, liberation, slow wean, and discontinuations are used when discussing the concept of discontinuing a patient from a mechanical ventilator. It is relatively easy with some patients. All it takes is simply testing their ability to breathe on their own, disconnecting the ventilator, and extubating them. However, weaning, the reduction of ventilatory support for a patient, is a process. Timing is everything when discontinuing ventilatory support or weaning. If the ventilatory support is stopped and the patient is extubated too soon, the risks are reintubation and the adverse effects associated with it. However, the potential for ventilator-associated pneumonia (VAP), a lower respiratory tract infection that develops more than 48 to 72 hours after endotracheal (ET) intubation, or even death must be considered as adverse effects of leaving a patient on the ventilator too long. This chapter will discuss the aspects of discontinuing ventilatory support.



» Skill Check Lists


25-1 Implementing a Spontaneous Breathing Trial


Supporting a patient during an exacerbation of a chronic pulmonary condition or an acute pulmonary illness at times requires mechanical ventilation. It is not, however, without consequences. These could range from airway damage such as tracheal stenosis to ventilator dependence, defined as the need for ventilatory support for lengthy periods, usually longer than 2 weeks. Discontinuing ventilatory support is a complex issue. Both premature discontinuation and delayed discontinuation of ventilatory support are associated with adverse patient outcomes. A way to test a patient’s readiness for successful discontinuation of mechanical ventilatory support is a SBT. Extubation should be considered but not integrated into the SBT process. Guidelines for extubation are provided in Box 25-1. The following is the step-by-step process for a spontaneous breathing trial.



Box 25-1


Practical Guidelines for Extubation




• No immediate need for mechanical ventilation or intubation exists.


• The medical course does not suggest impending respiratory failure or other indications for mechanical ventilation.


• Procedures necessitating intubation and general anesthesia are not immediately planned.


• Adequate oxygenation and ventilation with spontaneous ventilation have been achieved.


• The patient’s FiO2 requirement can be achieved with a mask or nasal cannula.


• The patient no longer needs mechanical ventilatory assistance.


• Weaning is successful.


• Minimal risk of upper airway obstruction exists.


• The patient has minimal edema or mass encroachment of the oropharynx and upper airway; oral and upper airway anatomy is otherwise normal.


• The result of a “cuff-leak” test is positive.


• Airway protection is adequate, and risk of aspiration is minimal.


• Level of consciousness and neuromuscular function allow gag reflex and adequate cough.


• Gastric contents are minimized by discontinuation of tube feedings for 4 to 6 hours before extubation.


• Clearance of pulmonary secretions is adequate.


• Level of consciousness and muscular strength allow effective coughing.


• Secretion volume and thickness are not worsening.


From Kacmarek RM, Stoller JK, Heuer AJ: Egan’s fundamentals of respiratory care, ed 10, St. Louis, MO, 2013, Mosby.




Implementation




1. Place the patient in a comfortable position.


2. Assess vital signs.


3. Assess the patient for SBT readiness, including the following:



4. Record the patient’s baseline values:



5. Advise the patient when the SBT will commence.


6. Change the ventilator to a spontaneous mode with zero pressure support ventilation (PSV) and zero continuous positive airway pressure (CPAP):



7. Maintain the fractional inspired oxygen (FiO2) that the patient was receiving on mechanical ventilation.


8. Monitor and record the SBT start data, including the following:


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Jun 12, 2016 | Posted by in RESPIRATORY | Comments Off on Discontinuing Ventilatory Support

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